What is the Diagnosis of Fever?

By Dr Poonam Sachdev
, Expert Content

Aug 11, 2011

543214.8 / 5(4 Ratings)

Fever is a symptom and not a disease and can be caused due to several reasons such as infection with bacteria or virus, medications, inflammation and injury. Your doctor will take a detailed history, examine you and then recommend tests based on the probable cause (infectious or non-infectious cause). Read to know how to diagnose fever and how to take fever.

How to Take Fever

Fever can be measured orally, rectally or in the axillary region with a thermometer. Oral measurement of temperature is the standard place for measuring fever and is most convenient as well. The thermometer is kept under the back of the tongue to take the temperature. Fever can be taken rectally with the same instrument. The rectal temperatures are generally higher than oral temperature and this temperature is closer to body core temperature. Fever taken by measuring temperature in the axillary region, or under the arm, is the least accurate. Axillary temperatures are usually 1°F less than oral temperature. So if you take temperature in the axillary region add one degree, and if rectally, subtract one degree.

Digital thermometers are easy to use and can measure temperatures quickly, usually in less than 30 seconds, and can be used for rectal, oral, or axillary readings. There is a "beep" when the measurement is complete, and the body temperature is displayed in numbers (Centigrade or Fahrenheit) on a small screen. These thermometers are not expensive, are easy to use and reliable. Mercury thermometers are inexpensive but its use is not recommended as there is a risk of accidental exposure to toxins and it is also slow (needs 2-3 minutes for a measurement).

According to experts fever strips are not recommended. The temperature readings with fever strips are not as accurate as other methods. Ear canal temperatures can be taken to measure fever. It is taken with an infrared probe and these devices are becoming increasingly popular. But if you have an existing ear infection/condition (otitis media) the fever reading can be wrong.

Blood tests (such as CBC with differential, blood electrolyte levels, and blood culture). Blood tests are also done to assess if there is infection and if it is a bacterial infection then the antibiotic sensitivity of the germ is also assessed.

Urinalysis: To rule out urinary tract infection.

X-rays of the abdomen, ultrasonography of abdomen to detect problems such as enteritis and abscess.

Computed tomography scan (CT scan) or magnetic resonance imaging scan (MRI scan) of the brain or any other part of the body as required.

Your doctor will not recommend all the tests at a time. Tests are done based on the duration of fever and associate symptoms.

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